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Just 'cause the heat pump can't do the whole job at that temp doesn't make it worthless or un-economical. What heat it produces at 22 is probably still cheaper than that they could get out of the furnace.

I agree that it needs checking, that temperature rise doesn't sound right. If it's not a problem with the heat pump itself, might be ductwork losses or a return leak in unconditioned space. Either way you should have more than a 6 degree rise no matter where you measure it.

I should point out that it's highly unlikely that your furnace output is 40k/80k. If the high fire rating is 80k, low fire is probably more like 55k. I don't know of any furnace but the Rheem modulating unit that can run at half its full capacity.

The posts so far have given me some clues. But, my heat pump readings are causing me more grief. As I look into the problem more and perform more measurements, I get results that make no sense. I started using more than one thermometer because I was beginning to suspect that the first one I used was giving irregular readings. So, I started using 3 thermometers. But this was another dead end. All thermometers give the same readings. But on Saturday, on one occasion, with a room temperature of 64F and an outside temperature of 21F, I got a temperature rise of 19F at the register. I had never seen this before. On Sunday, with a room temperature of 66F and an outside temperature of 23F, I got a 15F rise at the register. And, with an outside temperature of 32F and a room temperature of 62F, I got a rise of 16F. These situations were outside the norm. I usually get a temperature rise of 6 to 10 degrees.

I am beginning to wonder if there is a control problem. I have noticed two things: 1) the temperature rise of 19F happened after the heat pump had been running continuously for about 25 minutes and I achieved this by disabling the furnace. 2) On a defrost cycle I noticed that the heat pump stopped the defrost and returned to heat mode when there was still ice on the outside heat exchanger. I guess that the defrost period has to be increased, if that is possible, to clear the coils.

Outside temperature is thus appearing as less the culprit, given that the highest rise occured at the coldest test outside temperature.

My neighbour has an Hitachi heat pump and gets a constant 29F at the register, regardless what the outside temperature is (within the test range of over 20F outside temperature). Maybe I should have bought Japanese.

Service is a problem. I am not sure that my dealer knows enough. My description of the unusual readings goes right over his head. The only problem for me is that the heat pump is not heating the house most of the time, with below 32F and above 20F temperatures. There is a limiter that prevents the heat pump from continuing to run if the requested temperature is not reached within something like 10 to 15 minutes. When this happens the heat pump shuts down and the furnace starts. So, the optimum run time, over 25 minutes, is not reached. But, why should a heat pump produce more heat after running for 25 minutes than it produces when only running 10 minutes?

[QUOTE]Originally posted by mpagnan But on Saturday, on one occasion, with a room temperature of 64F and an outside temperature of 21F, I got a temperature rise of 19F at the register. I had never seen this before. I usually get a temperature rise of 6 to 10 degrees.

Originally posted by mpagnan the temperature rise of 19F happened after the heat pump had been running continuously for about 25 minutes and I achieved this by disabling the furnace.

There is a limiter that prevents the heat pump from continuing to run if the requested temperature is not reached within something like 10 to 15 minutes. When this happens the heat pump shuts down and the furnace starts. So, the optimum run time, over 25 minutes, is not reached.

Well, I think that I may have discovered something that explains the whole situation. My York heat pump has a jumper that sets the unit in one of two modes. The first is "normal operation" and the second is "hot heat pump". According to the manual the unit is shipped with the "normal operation" on. In this mode, the furnace fan comes on as soon as the heat pump starts. In "hot heat pump" mode, a 10 minute timer is started. After 10 minutes, the control will test the "liquid line temperature". If it over a threshold (the manual does not say what this is) then the fan will come on. Otherwise, the fan will stay off and another timer will be set. When the fan starts, the control will test the temperature every 30 seconds and if the temperature is over the threshold, increase fan speed. Or, if the temperature is below the threshold, reduce the fan speed.

I guess this will get me the higher output temperature at the register, but does it make sense to use it? Even if the temperature rise is only a few degrees during the first 20 minutes or so, am I still not getting the heat captured. Or, would it be more efficient to let the heat pump warm up the "liquid" before milking it for heat? Any suggestions?

For hot heat pump to work, the Y2 out must be connected to the indoor VS blower control board.

The blower starts in low heat speed every time that the outdoor ambient is under 50°. After the 10 minute timer expires, it checks the liquid line temp, and if it is over a temp the control will speed the indoor fan up.

If the outdoor temp is above 50° the blower starts on high speed every time.

BUT, the blower starts almost imediately every time weather hot heap pump is turned on or not.

I suggest you leave it turned off, until you have your contractor come out and wire your unit up to use that feature.
Or youo will have lock out troubles.

Originally posted by beenthere The blower starts in low heat speed every time that the outdoor ambient is under 50°. After the 10 minute timer expires, it checks the liquid line temp, and if it is over a temp the control will speed the indoor fan up.

That's a nice feature, since most folks I know who "hate" heat pumps complain of getting blasted with cold air when the unit cycles on. I keep trying to tell them it doesn't have to be that way.